As someone who's been using these for years
It's about time the world started to notice.
Marvell's kirkwood architecture at 1.2GHz is already powerful and fast enough to make decent client machines, browse the web a bit, serve up media to the telly and play some a bit of music. And all for a few miserly watts.
By the time these clock double and stack multiple cores on a single chip, there's next to no reason they shouldn't be used in a datacenter.
Supercomputers, perhaps not yet, but FLOPs-per-inch have got to be approaching x86, and FLOPs-per-watt must be ahead already.